An ECU upgrade affects a broad range of motor performance. Therefore comparing before and after results cannot be summed up by a single number. Max HP and max toque will not be enough; we need to look at the entire graph of performance over the broad RPM range.
September 2008 Archives
Here's instructions for removing and replacing the ECU. These instructions are specific to the E9x M3's and will be slightly different on E9x 335's.